Our central air unit is about 5 years old. I don't know the brand because we don't have a manual and the name plate is missing from the unit (?) Anyway, it was working perfectly until last night. I was sitting in the family room and all of a sudden I heard kind of a strange noise and the lights dimmed. Everything seemed fine after that and the fan was still blowing air out of the vents. It wasn't until this morning that I realized the ac wasn't working, only the inside blower unit. I flipped the breakers twice and no change. I even shut the unit off and had my daughter turn it on while I was standing outside. I did not hear a click or any type of noise. There are small tree droppings at the bottom of the unit, but nothing that looks like it would have stopped the unit. It's obvious something happened when the lights dimmed, but what?

Any ideas? It's really hot in here...

Update:
Ok, I finally discovered the giant electrical box outside was for the ac unit. Shut it off, opened it up and one of the two 30 amp fuses was blown. We replaced it and turned everything back on. The air coming out of the vents seemed a little cooler, but still not as cool as usual. We went outside and the ac unit was not running. Then while we were standing there trying to figure it out the unit came on and the fan started turning. It has been running for the last two hours, but still does not seem to be running as cold as usual. It has taken two hours to drop two degrees. Does that seem normal?

Do central air units normally need to be recharged or anything? How long should a system last?

(quote) Do central air units normally need to be recharged or anything? How long should a system last?

No,they shouldn`t need recharged unless there is a leak
(the do need serviced on a regular bases ;maybe once a year)
With care the average life of a airconditioner can be up to around 20 to 30 years